Suspension devices of the initially described type can be used, for example, although certainly not exclusively, in trucks, agricultural vehicles, or heavy-duty vehicles to decouple the driver's cab from the vehicle chassis, with respect to vibrations and motions, to the greatest extent possible.
Since high spring and damping rates must be selected for the spring/damper units of the chassis in heavy-duty vehicles due to considerable vehicle weights and large unsprung masses in the chassis, road irregularities or vibrations originating in axles and the drive train are still often transferred, to a considerable extent, via the axle suspension to the chassis and, from there, to the driver's cab.
In order to minimize the transfer of such impacts and vibrations to the driver's cab and thereby improve ergonomics and the driver's occupational safety, driver's cab suspensions have been developed in which the driver's cab is supported by a separate suspension system on the vehicle chassis. Such suspension systems for the driver's cab can be designed with lower spring rates than the axle suspension since the mass of the driver's cab is much less than that of the vehicle, and therefore road irregularities and/or vibrations originating in the drive train or axles of the vehicle can be much better isolated from the driver's working space due to such relatively soft cab suspension systems.
In the case of elastic cab suspension devices of the type in question, in order to limit undesired lateral motions or rolling of the driver's cab relative to the vehicle chassis—which occur, for instance, when driving on an incline or around a corner, or driving over irregularities present on only one side of the road—suspension devices have been developed in which a Watt's linkage system is disposed between the driver's cab and the chassis. Depending on the embodiment thereof, the Watt's linkage system prevents the driver's cab from moving laterally relative to the chassis, and ensures that spring compression movements of the cab relative to the chassis are substantially linear, i.e. the Watt's linkage system reduces the degrees of freedom of movement between the cab and the chassis to a vertical spring compression movement in particular.
Such a suspension device is known from DE 10 2005 043 998 A1, for example. Depending on the embodiment, this known suspension device comprises one or more Watt's linkages which reduce the degrees of freedom of movement of the cab relative to the chassis of a truck, for example, to a vertical motion only, and/or prevent rolling motions of the cab relative to the chassis. At the same time, linear spring compression movements between the cab and the chassis along the vertical axis can continue unrestricted, within the limits of cab spring displacement.
The coupling utilized in this known suspension device, which is largely fixed with respect to rolling motions between the cab and the chassis, offers the advantage in particular that independent rolling motions of the cab relative to the chassis can be prevented. However, this also causes the driver's cab to inevitably follow every roll-inducing motion coming from the chassis. When that occurs, the roll angle of the driver's cab is at least as great as the angle of the roll-inducing motion coming from the chassis, although it is often even greater, due to elasticities in the driver's cab mounting and the Watt's linkages.
Cornering or driving on an incline, or over irregularities present on only one side of the road, can cause the driver's cab to tilt to the same extent as the vehicle chassis, or even more. For reasons of comfort and safety, it would be desirable to prevent or at least reduce lateral inclinations of the driver's cab under all driving conditions. Furthermore, the driver's comfort would be greatly enhanced if the transfer of the inclination of the chassis to the driver's cab could be prevented or reduced e.g. when a truck is parked transversely to an incline.